Sunday 30 June 2013 04.00 EDT
First published on Sunday 30 June 2013 04.00 EDT

As government becomes more open and transparent, we are all increasingly asked to help shape policy decisions. Issues ranging from fracking to three-parent babies and genetically modified crops are all difficult, so how should we negotiate a tangle of often conflicting and technical complexities to produce the best policy decisions?

Many of the issues have a scientific element and a social science element. They involve politics, religious preferences, economic considerations and ethical concerns. We need debate and it must be based as much on listening as talking: the differing views of individuals have to be heard and their concerns addressed. Questions should not go unanswered, or if they cannot be answered that needs to be acknowledged. What is key is reliable evidence, and if the evidence does not exist it has to be researched.

It should be remembered that there is rarely a right or wrong answer on these sorts of issues, although some people of faith who deal more in moral absolutes might disagree with me. There are always people who have 100% conviction in their views but, as a general rule, when society is looking for the best outcome it should take such absolutist views with a pinch of salt. If you start out with certainties you are unlikely to have considered all the evidence or maybe any of the evidence.

So evidence is where we should start. Sadly, scientific evidence was not much to the fore 10 years ago when we debated genetically modified crops in the UK. Scientists tended to hang back while big corporations battled it out with anti-capitalists and environmentalists. Opinions were thrown around as if they were facts. The debate became toxic, with people often forming their decisions based on who shouted the loudest. There were echoes of that recently when GM hit the headlines and some people yet again rolled out the trite "Frankenstein foods" nonsense. If we want to make the best decisions, those opinions should only bear weight if they are evidence-based.

We need to base our debate on high-quality scientific advice, which is dependent upon high-quality science. Good science is a reliable way of generating knowledge because of the way that it is done. It is based on reproducible observation and experiment, taking account of all evidence and not cherry-picking data. Scientific issues are settled by the overall strength of that evidence combined with rational, consistent and objective argument. Central to science is the ability to prove that something is not true, an attribute which distinguishes science from beliefs based on religions and ideologies, which place more emphasis on faith, tradition and opinion.

A good scientist is inherently sceptical – the Royal Society's motto, in Latin of course, roughly translates as "take nobody's word for it". We have to make sure that those making policy decisions begin by having timely access to all the relevant scientific evidence in as easy to understand a format as possible. That puts a responsibility on scientists to engage effectively and straightforwardly with society.

So where would that leave us on fracking for example – what can the science tell us? Thanks to the British Geological Survey we have a reasonably good idea about how much shale gas there is and we have to assess how much of it we can get out of the ground. Crucially, we need to assess the health, safety, and local and global environmental risks, some of which was done by the Royal Society and Royal Academy of Engineering last year.

These analyses and assessments are essential but are only the start of the debate. We need to discuss energy security and affordability – people want to know if household fuel bills can be brought down. Those living in areas where there might be fracking have a major stake in the decision. They are the ones who will have a big industry moving into their neighbourhoods, and they need to weigh up the disruption and potential risks against the potential economic benefits for themselves locally and for the UK as a whole. These are questions that are not easily answered, but what is key is to get the science right first before moving on to the politics.

We must, of course, also recognise the limitations on the scientific evidence. Science is not etched in stone, it evolves. Early on in a scientific study knowledge is often tentative, and only after repeated, rigorous testing does it become increasingly secure. It is this process that makes science reliable, but it can take time. This can lead to problems when scientists are called upon to give advice on issues when the science is not yet complete. Sometimes scientists or the media can oversimplify or even overstate the case but where that happens it devalues scientific evidence. The public wants clear and simple answers but sometimes that is not possible, and when it is not possible scientists have to say so.

To make the best policy decisions we need to start with all the evidence that we can gather. It must be presented openly and honestly, particularly recognising any uncertainties. Once that is established we can introduce the economic, political, religious and other factors that influence people's decision-making. Ideally the public debate, and here the media have a major responsibility, would then be carried out in a rational way seeking the best outcome.

The government's decision to give the go-ahead to doctors to produce IVF babies who have a tiny bit of mitochondrial DNA from a third "parent" to prevent some major childhood diseases is a good example of how to manage a policy issue involving science. The science was assessed and then the ethical concerns weighed up against the potential benefits.

Here in the UK we are quite enlightened and, as a result, we are actually pretty good at making sensible policy decisions involving science. Another example is climate change. Although lobbyists try to influence the agenda and sometimes have success in influencing public opinion, successive governments have listened to the consensus view of expert climate scientists and taken action.

We must not be complacent, but in the UK, scientific advice for public policy is handled better than in many other countries. It is usually the basis upon which politicians, economists, ethicists and others develop their views – first the facts, then the opinions.

We seem to have an inbuilt capacity for rationality and a distrust of dogma – it is probably what keeps us as a world leader in science. If we can keep that alive we will do well and more often than not make good policy.